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Abstract:

A method of fabricating an organic EL display apparatus includes:
obtaining a representative current (I)-voltage (V) characteristic of a
display panel including pixels each having an organic EL device and a
driving transistor; dividing the display panel into a plurality of
divided regions, and calculating a light-emitting efficiency and an
offset luminance value for each of the divided regions calculated by an
I-luminance (L) characteristic of the divided region; measuring luminance
of light emitted from each of the pixels and calculating an L-V
characteristic of each of the pixels; calculating an L-V characteristic
of each divided region by dividing each current value of the
representative I-V characteristic by light-emitting efficiency, and by
adding an offset luminance value; and calculating a correction parameter
for each pixel such that the L-V characteristic of each pixel is
corrected to the L-V characteristic of the divided region including the
pixel.

Claims:

1. A method of fabricating an organic EL display apparatus, comprising:
obtaining a representative current-voltage characteristic common to an
entire display panel including a plurality of pixels each having a
light-emitting device and a driving device which is voltage-driven and
controls a current supply to the light-emitting device; dividing the
display panel into a plurality of divided regions, applying voltage to
the driving device in each of the pixels, measuring a current flowing in
each of the divided regions and luminance of light emitted from the
divided region when the current is flowing in the divided region,
calculating a current-luminance characteristic of the divided region
according to the measured current flowing in the divided region and the
measured luminance of the light emitted from the divided region, and
calculating a light-emitting efficiency and a offset luminance value for
each of the divided regions, the light-emitting efficiency being a slope
of the current-luminance characteristic, and the offset luminance value
being an intercept of a luminance axis of the current-luminance
characteristic; measuring luminance of light emitted from each of the
pixels in the display panel by a predetermined measuring device and
calculating a luminance-voltage characteristic of each of the pixels
according to the measured luminance of the light emitted from the pixel;
calculating a luminance-voltage characteristic of each divided region by
multiplying each current value of the representative current-voltage
characteristic by light-emitting efficiency of each divided region, and
by adding, to the multiplied value, an offset luminance value calculated
for each divided region; and calculating a correction parameter for a
target pixel such that the luminance-voltage characteristic of the target
pixel calculated in the calculating of a luminance-voltage characteristic
of each pixel is corrected to the luminance-voltage characteristic of a
divided region to which the target pixel belongs to, the
luminance-voltage characteristic of the divided region being calculated
in the calculating of a luminance-voltage characteristic of each divided
region.

2. The method of fabricating the organic EL display apparatus according
to claim 1, wherein, the measuring of luminance of the light emitted from
the pixel includes; applying a predetermined voltage to the pixels
included in the display panel such that the pixels emit light
simultaneously; and capturing, by a predetermined measuring device, the
light simultaneously emitted from the pixels; and in the calculating of a
luminance-voltage characteristic, an image obtained by the capturing is
obtained, luminance of each of the pixels is determined from the obtained
image, and the luminance-voltage characteristic of each of the pixels is
calculated using the predetermined voltage and the determined luminance
of the pixel.

3. The method of fabricating the organic EL display apparatus according
to claim 2, wherein the predetermined measuring device is an image
sensor.

4. The method of fabricating the organic EL display apparatus according
to claim 2, wherein, in the calculating of a current-voltage
characteristic of each pixel, a position of the target pixel in the
display panel is determined, and when the target pixel is located near a
boundary with another neighboring divided region which does not include
the target pixel, the light-emitting efficiency and the offset luminance
value of the target pixel are calculated by weighting the light-emitting
efficiency and the offset luminance value of the divided region which
includes the target pixel and the light-emitting efficiency and the
offset luminance value of the other neighboring divided region at a
predetermined ratio, and a target luminance-voltage characteristic of the
target pixel for calculating a correction parameter of the target pixel
is calculated by multiplying each current value of the representative
current-voltage characteristic by the light-emitting efficiency of the
target pixel, and by adding the offset luminance value of the target
pixel to the multiplied value, in the calculating of a correction
parameter, a correction parameter for the target pixel is calculated such
that the luminance-voltage characteristic of the target pixel calculated
in the calculating of a luminance-voltage characteristic of each pixel is
corrected to the target luminance-voltage characteristic of the target
pixel calculated in the calculating of a target luminance-voltage
characteristic.

5. The method of fabricating the organic EL display apparatus according
to claim 4, wherein, in the calculating of a current-voltage
characteristic of each pixel, when calculating the light-emitting
efficiency and the offset luminance value of the target pixel, the closer
the target pixel to the boundary with the other neighboring divided
region, the higher a ratio of the light-emitting efficiency and the
offset luminance value of the other neighboring divided region used for
the weighting.

6. The method of fabricating the organic EL display apparatus according
to claim 5, wherein, in the calculating of a current-voltage
characteristic of each pixel, when calculating the light-emitting
efficiency and the offset luminance value of the target pixel, the
light-emitting efficiency and the offset luminance value of the target
pixel are calculated according to a ratio between a distance from the
target pixel to the center of the divided region including the target
pixel and a distance from the target pixel to the center of each of the
other neighboring divided region.

7. The method of fabricating the organic EL display apparatus according
to claim 1, wherein, in the calculating of a light-emitting efficiency
and a offset luminance value, the light-emitting efficiency and the
offset luminance value calculated in a method of fabricating another
organic EL display apparatus fabricated under a same condition is used as
the light-emitting efficiency and the offset luminance value of each of
the divided regions.

8. The method of fabricating the organic EL display apparatus according
to claim 1, wherein, in the obtaining of a representative current-voltage
characteristic, a representative current-voltage characteristic obtained
in a method of fabricating another organic EL display apparatus
fabricated under a same condition is used as the representative
current-voltage characteristic.

9. The method of fabricating the organic EL display apparatus according
to claim 1, further comprising writing, on a predetermined memory used
for the display panel, the correction parameter for each pixel calculated
in the calculating of a correction parameter.

10. The method of fabricating the organic EL display apparatus according
to claim 1, wherein, in the obtaining of a representative current-voltage
characteristic, a plurality of voltages are applied to a plurality of
pixels to be measured to flow current in the pixels to be measured, the
current flowing in each of the pixels to be measured is measured for each
of the voltages, and the representative current-voltage characteristic is
calculated by averaging the current-voltage characteristics of the pixels
to be measured.

11. The method of fabricating the organic EL display apparatus according
to claim 1, wherein, in the obtaining of a representative current-voltage
characteristic, a plurality of common voltages are simultaneously applied
to the pixels to be measured to flow current in each of the pixels to be
measured, a sum of the current flowing in the pixels to be measured is
calculated for each of the common voltages, and the representative
current-voltage characteristic is calculated by dividing the sum of the
current flowing in the pixels to be measured by the number of the pixels
to be measured.

12. The method of fabricating the organic EL display apparatus according
to claim 1, wherein a correction parameter includes a parameter
indicating a ratio of a voltage of the luminance-voltage characteristic
of the target pixel calculated in the calculating of a luminance-voltage
characteristic to a voltage of the luminance-voltage characteristic of
the divided region including the target pixel calculated in the
calculating of a luminance-voltage characteristic of each divided region.

13. The method of fabricating the organic EL display apparatus according
to claim 1, wherein a correction parameter includes a parameter
indicating a ratio of a luminance of the luminance-voltage characteristic
of the target pixel calculated in the calculating of a luminance-voltage
characteristic to a luminance of the luminance-voltage characteristic of
the divided region including the target pixel calculated in the
calculating of a luminance-voltage characteristic of each divided region.

14. The method of fabricating the organic EL display apparatus according
to claim 1, wherein a correction parameter includes a parameter
indicating a difference between a voltage of the luminance-voltage
characteristic of the target pixel calculated in the calculating of a
luminance-voltage characteristic and a voltage of the luminance-voltage
characteristic of the divided region including the target pixel
calculated in the calculating of a luminance-voltage characteristic of
each divided region.

15. The method of fabricating the organic EL display apparatus according
to claim 1, wherein the representative current-voltage characteristic and
the luminance-voltage characteristic are a representative characteristic
between a current and a voltage signal and a characteristic between a
luminance and a voltage signal, respectively.

16. An organic EL display apparatus comprising: a plurality of pixels
each including a light-emitting device and a driving device for
controlling a current supply to the light-emitting device; a plurality of
data lines for supplying a signal voltage to each of the pixels; a
plurality of scanning lines for supplying a scanning signal to each of
the pixels; a data line driving circuit for supplying the signal voltage
to the data lines; a scanning line driving circuit for supplying the
scanning signal to the scanning lines; a storage unit configured to store
predetermined correction parameters for each of the pixels; and a
correction unit configured to read, from the storage unit, the
predetermined correction parameters corresponding to each of the pixels
to correct the video signal corresponding to each of the pixels, when an
input of a video signal is provided from outside, wherein the
predetermined correction parameters are generated by the following:
obtaining a representative current-voltage characteristic common to an
entire display panel including the pixels; dividing the display panel
into a plurality of divided regions, applying voltage to the driving
device in each of the pixels, measuring a current flowing in each of the
divided regions and luminance of light emitted from the divided region
when the current is flowing in the divided region, calculating a
current-luminance characteristic of the divided region, and calculating a
light-emitting efficiency and an offset luminance value for each of the
divided regions, the light-emitting efficiency being a slope of the
current-luminance characteristic, and the offset luminance value being an
intercept of a luminance axis of the current-luminance characteristic;
measuring luminance of light emitted from each of the pixels in the
display panel by a predetermined measuring device and calculating a
current-voltage characteristic of each of the pixels; calculating a
luminance-voltage characteristic of each divided region by multiplying
each current value of the representative current-voltage characteristic
by light-emitting efficiency of each divided region, and by adding, to
the multiplied value, a offset luminance value calculated for the divided
region; and calculating a correction parameter for a target pixel for
correcting the luminance-voltage characteristic of the target pixel to
the luminance-voltage characteristic of a divided region to which the
target pixel belongs to, the luminance-voltage characteristic of the
divided region being calculated in the calculating of a luminance-voltage
characteristic of each divided region.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001] This is a continuation application of PCT application No.
PCT/JP2011/000840 filed on Feb. 16, 2011, designating the United States
of America.

[0005] An image display apparatus using organic EL devices (organic EL
display) has been known as an image display apparatus using
current-driven light-emitting devices. The organic EL display has been
attracting attention as a possible next-generation Flat Panel Display
(FPD) for its advantages including wide viewing angles and small power
consumption.

[0006] In an organic EL display, the organic EL devices composing pixels
are usually arranged in a matrix. An organic EL display in which organic
EL devices are provided at cross-points of row electrodes (scanning
lines) and column electrodes (data lines), and the organic EL devices are
driven by applying voltage corresponding to data signal between a
selected row electrode and column electrodes is referred to as a
passive-matrix organic EL display.

[0007] In contrast, an organic EL display in which thin film transistors
(TFT) are provided at cross-points of the scanning lines and the data
lines, a gate of a driving transistor is connected to the TFT, the data
signal input is provided to the driving transistor by turning on the TFT
through the selected scanning line, and the organic EL devices are driven
by the driving transistors. Such an organic EL display is referred to as
an active-matrix organic EL display.

[0008] In contrast with the passive-matrix organic EL display in which the
organic EL devices connected to each row electrode (scanning line) emit
light only when the row electrode is selected, in the active-matrix
organic EL display, the organic EL devices can emit light until next
scanning (selection). Accordingly, even when the duty cycle increases,
the luminance of the display does not decrease. Thus, the display can be
driven by low voltage, reducing the power consumption. However, due to
variation in the characteristics of the driving transistors and the
organic EL devices, the active-matrix organic EL display has a
disadvantage that the luminance is uneven because luminance of the
organic EL device in each pixel is different even when the same data
signal is given.

[0009] Typical methods of compensating the unevenness in luminance due to
variation in the characteristics (hereafter referred to as uneven
characteristics) of the driving transistors and organic EL device caused
by the fabricating process in the conventional organic EL display include
compensation by complex pixel circuits and compensation using an external
memory.

[0010] However, the complex pixel circuits decreases yield. In addition,
the complex pixel circuits do not compensate the unevenness in the
light-emitting efficiency of the organic EL device in each pixel.

[0011] For the reasons described above, several methods of compensating
the unevenness in the characteristics of the pixels by the external
memory have been proposed.

[0012] For example, according to the electric optical device, the method
of driving the electric optical device, the method of fabricating the
electric optical device, and the electronic device according to Patent
Literature 1: Japanese Unexamined Patent Application Publication No.
2005-283816, in a current program pixel circuit, the luminance of each
pixel is measured by at least one type of input current, and the measured
luminance ratio of each pixel is stored in the storage capacitance, the
image data is corrected based on the luminance ratio, and the current
program pixel circuit is driven by the image data after the correction.
With this, the unevenness in luminance is suppressed, allowing a uniform
display.

SUMMARY OF THE INVENTION

[0013] However, with the solution described above, early measurement of
the luminance and the current is necessary for compensating the uneven
luminance using the external memory.

[0014] When performing the early measurement on the current and correcting
the uneven luminance, it is necessary to take a long time for the early
measurement in order to measure the desired current highly precisely
considering the parasitic capacitance of the entire circuit and the line
resistance. Accordingly, there is a problem that the fabricating cost
increases when the uneven luminance is compensated while maintaining the
precision of the correction. In particular, the larger the panel screen
and the more the number of input gray-scales, it takes longer to measure
the entire surface of the panel. As a result, there is a problem that the
fabricating cost is significantly increased.

[0015] Alternatively, when the uneven luminance is corrected by the early
measurement of the luminance with respect to the voltage input, instead
of the early measurement of the current in each pixel, the variations in
both the driving transistors and the organic EL devices are measured,
allowing the correction of both of the variations at once.

[0016]FIG. 19 illustrates an example of conventional correction method
for an organic EL display. Before correction, the organic EL display has
a luminance distribution reflecting both the luminance distribution due
to the organic EL device and the luminance distribution due to the
driving transistors. In contrast, with the conventional correction method
for measuring luminance with respect to a voltage input, both the
variations in the organic EL devices and the variations in the driving
transistors are corrected. Accordingly, the organic EL display after
correction has a uniform luminance distribution. However, in order to
obtain the uniform luminance distribution, the currents flowing in the
organic EL devices differ from pixel to pixel. In this case, the current
load on the organic EL device differ for each pixel, accelerating the
variation in the degradation of luminance due to the product life of the
organic EL devices, triggering the uneven luminance due to change over
time.

[0017] In view of the problems above, it is an object of the present
invention to provide an organic EL display apparatus and the method of
fabricating the organic EL display apparatus capable of reducing the
manufacturing cost for generating the uneven luminance correcting
parameter and suppressing the uneven luminance due to the change over
time.

[0018] In order to solve the problems described above, the organic EL
display apparatus according to an aspect of the present invention
includes obtaining a representative current-voltage characteristic common
to an entire display panel including a plurality of pixels each having a
light-emitting device and a driving device which is voltage-driven and
controls a current supply to the light-emitting device; dividing the
display panel into a plurality of divided regions, applying voltage to
the driving device in each of the pixels, measuring a current flowing in
each of the divided regions and luminance of light emitted from the
divided region when the current is flowing in the divided region,
calculating a current-luminance characteristic of the divided region
according to the measured current flowing in the divided region and the
measured luminance of the light emitted from the divided region, and
calculating a light-emitting efficiency and a offset luminance value for
each of the divided regions, the light-emitting efficiency being a slope
of the current-luminance characteristic, and the offset luminance value
being an intercept of a luminance axis of the current-luminance
characteristic; measuring luminance of light emitted from each of the
pixels in the display panel by a predetermined measuring device and
calculating a luminance-voltage characteristic of each of the pixels
according to the measured luminance of the light emitted from the pixel;
calculating a luminance-voltage characteristic of each divided region by
multiplying each current value of the representative current-voltage
characteristic by light-emitting efficiency of each divided region, and
by adding, to the multiplied value, an offset luminance value calculated
for each divided region; and calculating a correction parameter for a
target pixel such that the luminance-voltage characteristic of the target
pixel calculated in the calculating of a luminance-voltage characteristic
of each pixel is corrected to the luminance-voltage characteristic of a
divided region to which the target pixel belongs to, the
luminance-voltage characteristic of the divided region being calculated
in the calculating of a luminance-voltage characteristic of each divided
region.

[0019] According to the organic EL display apparatus and the method of
manufacturing the organic EL display apparatus, the current load of the
organic EL devices having a product life dependent on the light-emitting
current is set to be equal from pixel to pixel. Therefore, it is possible
to suppress the degradation in luminance caused by the product life.

[0020] Furthermore, upon generating the correction parameter, it is not
necessary to measure the current of each pixel. Thus, it is possible to
reduce the time necessary for measurement for generating the correction
parameter, and the fabrication cost can be reduced.

Further Information about Technical Background to this Application

[0021] The disclosure of Japanese Patent Application No. 2010-070961 filed
on Mar. 25, 2010 including specification, drawings and claims is
incorporated herein by reference in its entirety.

[0022] The disclosure of PCT application No. PCT/JP2011/000840 filed on
Feb. 16, 2011, including specification, drawings and claims is
incorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and other objects, advantages and features of the invention
will become apparent from the following description thereof taken in
conjunction with the accompanying drawings that illustrate a specific
embodiment of the invention. In the Drawings:

[0024] FIG. 1 is a block diagram illustrating an electric configuration of
the organic EL display apparatus according to Embodiment of the present
invention;

[0025] FIG. 2 illustrates an example of circuit configuration of a pixel
in the display unit and a connection with circuits around the pixel;

[0026]FIG. 3 is a functional block diagram of a fabricating system used
for the method of fabricating the organic EL display apparatus according
to the present invention;

[0027]FIG. 4 is an operational flowchart illustrating the method of
fabricating the organic EL display apparatus according to Embodiment 1 of
the present invention;

[0028] FIG. 5A illustrates charts for illustrating characteristics
obtained by the first process group in the method of fabricating the
organic EL display device according to Embodiment 1 of the present
invention;

[0029] FIG. 5B illustrates charts for illustrating characteristics
obtained by the second process group in the method of fabricating the
organic EL display device according to Embodiment 1 of the present
invention;

[0030]FIG. 6 illustrates charts for illustrating characteristics obtained
by the third process group in the method of fabricating the organic EL
display device according to Embodiment 1 of the present invention;

[0031]FIG. 7A is an operational flowchart illustrating the first specific
method for obtaining the representative I-V characteristics;

[0032]FIG. 7B is an operational flowchart illustrating the second
specific method for obtaining the representative I-V characteristics;

[0033]FIG. 8A is an operational flowchart illustrating a first specific
method for calculating the coefficients of I-L conversion equation of
each divided region;

[0034]FIG. 8B is an operational flowchart illustrating a second specific
method for calculating the coefficients of I-L conversion equation of
each divided region;

[0035]FIG. 9A is an operational flowchart illustrating the first specific
method for obtaining the L-V characteristics of each pixel;

[0036]FIG. 9B is a diagram for illustrating a captured image when
calculating the L-V characteristics of each pixel;

[0037] FIG. 10A is an operational flowchart illustrating the second
specific method for obtaining the L-V characteristics of each pixel;

[0038] FIG. 10B is a diagram for describing a captured image when
calculating the L-V characteristic of each pixel;

[0039] FIG. 10C is a state transition diagram of the measured pixels that
are selected;

[0040]FIG. 11 is a diagram for illustrating a method of weighting
coefficients of pixels at the boundary of the divided regions;

[0041]FIG. 12A is a graph illustrating luminance-voltage characteristic
when calculating correction values for voltage gain and voltage offset in
a method of fabricating the organic EL display apparatus according to
Embodiment 1 of the present invention;

[0042]FIG. 12B is a graph illustrating luminance-voltage characteristic
when calculating a correction value for current gain in a method of
fabricating the organic EL display apparatus according to Embodiment 1 of
the present invention;

[0043]FIG. 13A is a graph indicating the amount of offset and offset
width when a correction parameter is generated in the conventional
fabrication method;

[0044]FIG. 13B is a graph indicating the amount of offset and the offset
width when a correction parameter is generated in the method of
fabricating the organic EL display apparatus according to Embodiment 1 of
the present invention;

[0045]FIG. 14 illustrates the effect of the organic EL display apparatus
corrected by the method of fabricating the organic EL display apparatus
according to the present invention;

[0046] FIG. 15A indicates luminance distribution on a display panel when
the light-emitting layer is formed by vapor deposition;

[0047] FIG. 15B indicates the luminance distribution on the display panel
when the light-emitting layer is formed by inkjet printing;

[0048]FIG. 16 illustrates the operations for correcting the voltage gain
and the offset at the time of display operation of the organic EL display
apparatus according to Embodiment 2 of the present invention;

[0049] FIG. 17 illustrates the operations for correcting the current gain
at the time of display operation of the organic EL display apparatus
according to Embodiment 2 of the present invention;

[0050]FIG. 18 is an external view of a thin flat TV incorporating the
organic EL display apparatus according to the present invention; and

[0051]FIG. 19 is a diagram for illustrating the effect of the organic EL
display apparatus corrected by the conventional correction method.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0052] The method of fabricating an organic EL display apparatus according
to an aspect of the present invention includes obtaining a representative
current-voltage characteristic common to an entire display panel
including a plurality of pixels each having a light-emitting device and a
driving device which is voltage-driven and controls a current supply to
the light-emitting device; dividing the display panel into a plurality of
divided regions, applying voltage to the driving device in each of the
pixels, measuring a current flowing in each of the divided regions and
luminance of light emitted from the divided region when the current is
flowing in the divided region, calculating a current-luminance
characteristic of the divided region according to the measured current
flowing in the divided region and the measured luminance of the light
emitted from the divided region, and calculating a light-emitting
efficiency and a offset luminance value for each of the divided regions,
the light-emitting efficiency being a slope of the current-luminance
characteristic, and the offset luminance value being an intercept of a
luminance axis of the current-luminance characteristic; measuring
luminance of light emitted from each of the pixels in the display panel
by a predetermined measuring device and calculating a luminance-voltage
characteristic of each of the pixels according to the measured luminance
of the light emitted from the pixel; calculating a luminance-voltage
characteristic of each divided region by multiplying each current value
of the representative current-voltage characteristic by light-emitting
efficiency of each divided region, and by adding, to the multiplied
value, an offset luminance value calculated for each divided region; and
calculating a correction parameter for a target pixel such that the
luminance-voltage characteristic of the target pixel calculated in the
calculating of a luminance-voltage characteristic of each pixel is
corrected to the luminance-voltage characteristic of a divided region to
which the target pixel belongs to, the luminance-voltage characteristic
of the divided region being calculated in the calculating of a
luminance-voltage characteristic of each divided region.

[0053] When calculating the luminance-voltage characteristic of each pixel
by measuring the luminance of light emitted from each pixel included in
the display panel, the luminance-voltage characteristic of each pixel
reflects both the variations in the light-emitting device and a TFT which
is the driving device for driving the light-emitting device included in
each pixel.

[0054] When the correction parameter for correcting both the variations in
the light-emitting devices and the variations in the TFTs, and the video
signal from outside is corrected using the correction parameter, the
correction includes a correction for the variations in the light-emitting
devices. Accordingly, with this correction, the luminance of the light
emitted from the light-emitting device is uniform with respect to the
video signal in the same gray-scale for the entire display panel.

[0055] However, due to the variations in the characteristics of the
light-emitting devices, the luminance of each light-emitting device
differs when the same current flows. Thus, when the correction for making
the luminance of the light-emitting devices is uniform for the entire
display panel, the amount of current flowing in each light-emitting
device differs from the light-emitting device to the light-emitting
device. In this case, since the product life of the light-emitting device
depends on the amount of current, the product life of each light-emitting
device differ as the time passes. The variation in product life of each
light-emitting device consequently appears as uneven luminance on screen.

[0056] Accordingly, in this aspect, only the variations in TFTs are mainly
corrected, and the amount of the current flowing in each light-emitting
device is uniform for the video signal with the same gray-scale for the
entire display panel. This is because, although the variations in the
TFTs are large, the variations in the light-emitting devices are very
small among the light-emitting devices, and thus correcting only the
variations in the TFTs enables displaying of a uniform image to human eye
without correcting variations in the light-emitting devices.

[0057] In this aspect, first, the representative current-voltage
characteristic common to all of the pixels in the display panel is set.
Next, the luminance when the current flows in the divided region is
measured for each divided region, and the light-emitting efficiency and
the offset luminance value of each divided region are calculated. Here,
the offset luminance value is a luminance value in which a
current-luminance straight line having a slope equal to the
light-emitting efficiency crosses a luminance axis having a current value
of zero. More specifically, the variations in the light-emitting devices
are specified from the difference in the light-emitting efficiencies and
the offset luminance values in the divided regions.

[0058] Next, the luminance of the light emitted from each pixel included
in the display panel is measured by the predetermined measuring device,
and the luminance-voltage characteristic of each pixel is calculated.

[0059] Subsequently, the luminance-voltage characteristic of each divided
region is calculated by multiplying the measured light-emitting
efficiency of each divided region by the current value of the
representative current-voltage characteristic, and by adding the measured
offset luminance value for each divided region to the multiplied value.

[0060] After that, the correction parameter is calculated such that the
luminance-voltage characteristic of each pixel is corrected to the
luminance-voltage characteristic of each divided region. With this, the
current-voltage characteristic of each divided region is corrected to the
representative current-voltage characteristic common to the entire
display panel.

[0061] More specifically, the luminance-voltage characteristic of the
divided region which includes the target pixel is the characteristic
including the variation in the light-emitting device that has been
measured. Accordingly, calculating a correction parameter for correcting
the luminance-voltage characteristic of the target pixel to the
luminance-voltage characteristic of the divided region including the
target pixel is calculating a correction parameter for mainly correcting
the variation in the TFT which barely includes the variation in
light-emitting device. In other words, the correction parameter for
correcting the variation in the TFT excluding the variation in the
light-emitting devices is calculated.

[0062] With this, it is possible to set a constant current flowing in each
light-emitting device for the same specified gray-scale, making the
current load constant between the light-emitting devices. Thus, it is
possible to set a current flowing in each light-emitting device uniform,
suppressing the variation in the product life of the light-emitting
devices as time passes. As a result, it is possible to prevent the uneven
luminance due to the variations in the product life of the light-emitting
device from appearing on screen.

[0063] Furthermore, in this aspect, in order to obtain the correction
parameter for correcting the variation in TFT, the luminance-voltage
characteristic including both the variation in the light-emitting device
and the variation in the TFT in each pixel and the light-emitting
efficiency and the offset luminance value of the light-emitting devices
in each divided region are measured, instead of measuring the variations
in the TFTs in the pixels themselves. In other words, the light-emitting
efficiency and the offset luminance value of each divided region is
calculated by dividing the display panel into multiple divided regions,
and measuring the current flowing in the divided region and the luminance
of the divided region when the current is flowing in the divided region,
for each divided region. In other words, by calculating the
light-emitting efficiency and the offset luminance value of each divided
region, it is possible to clarify the variations in the light-emitting
devices between the divided regions. This is because the light-emitting
devices vary for a certain region, rather than for a pixel. Furthermore,
the voltage-luminance characteristics for multiple pixels can be measured
at the same time by using a CCD camera, for example. With this, compared
to the case in which the variation in the TFT is measured by applying
voltage to each pixel, and measuring the current flowing in each pixel,
it is possible to significantly reduce the time for measuring the
correction parameter. Furthermore, by not forcefully correcting the
luminance inclination which does not bother the user, the power
consumption can also be reduced.

[0064] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, it is preferable that
the measuring of luminance of the light emitted from the pixel includes;
applying a predetermined voltage to the pixels included in the display
panel such that the pixels emit light simultaneously; and capturing, by a
predetermined measuring device, the light simultaneously emitted from the
pixels; and in the calculating of a luminance-voltage characteristic, an
image obtained by the capturing is obtained, luminance of each of the
pixels is determined from the obtained image, and the luminance-voltage
characteristic of each of the pixels is calculated using the
predetermined voltage and the determined luminance of the pixel.

[0065] According to this aspect, when obtaining the luminance-voltage
characteristic for each pixel, the light simultaneously emitted from all
of the pixels in the light-emitting panel is captured at one time,
without capturing light emitted from each pixel by applying the
predetermined voltage. Subsequently, based on the captured image, the
luminance of the light emitted from each pixel is determined by image
processing separating the light emitted from each pixel. Accordingly, the
time for capturing image is significantly reduced. Thus, it is possible
to significantly simplify the process for obtaining the luminance-voltage
characteristic for each pixel defined in the step above.

[0066] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, it is preferable that
the predetermined measuring device is an image sensor.

[0067] According to this aspect, the image of light emitted from all of
the pixels can be obtained at low noise, high sensitivity, and high
resolution. Thus, it is possible to obtain highly precise
luminance-voltage characteristic of each pixel by image processing for
separating the light emitted from each pixel.

[0068] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the calculating of a
current-voltage characteristic of each pixel, a position of the target
pixel in the display panel may be determined, and when the target pixel
is located near a boundary with another neighboring divided region which
does not include the target pixel, the light-emitting efficiency and the
offset luminance value of the target pixel may be calculated by weighting
the light-emitting efficiency and the offset luminance value of the
divided region which includes the target pixel and the light-emitting
efficiency and the offset luminance value of the other neighboring
divided region at a predetermined ratio, and a target luminance-voltage
characteristic of the target pixel for calculating a correction parameter
of the target pixel may be calculated by multiplying each current value
of the representative current-voltage characteristic by the
light-emitting efficiency of the target pixel, and by adding the offset
luminance value of the target pixel to the multiplied value, in the
calculating of a correction parameter, a correction parameter for the
target pixel may be calculated such that the luminance-voltage
characteristic of the target pixel calculated in the calculating of a
luminance-voltage characteristic of each pixel is corrected to the target
luminance-voltage characteristic of the target pixel calculated in the
calculating of a target luminance-voltage characteristic.

[0069] When the correction parameter for each pixel included in the
divided region is calculated using only the light-emitting efficiency of
the divided region, and the video signal for each pixel is corrected, the
target luminance-voltage characteristic is different for each divided
region. Thus, there may be a possibility that the boundaries of the
divided regions reflecting the difference in the target luminance-voltage
characteristic appear, making it impossible to display a smooth image.

[0070] According to this aspect, the position of the target pixel is
located, and when the pixel is located near the boundary with the other
neighboring divided regions, the light-emitting efficiency and the offset
luminance value of the pixel are calculated based on the light-emitting
efficiency and the offset luminance value of the divided region including
the pixel and the light-emitting efficiency and the offset luminance
value of the other neighboring divided regions. Subsequently, the target
luminance-voltage characteristic as the target for calculating the
correction parameter for the target pixel is calculated for the target
pixel by multiplying each current value in the representative
voltage-current characteristic common to the entire display panel by the
light-emitting efficiency of the target pixel and by adding the offset
luminance value of the target pixel to the multiplied value, and the
correction parameter is calculated such that the luminance-voltage
characteristic of the target pixel is corrected to the target
luminance-voltage characteristic.

[0071] With this, the light-emitting efficiency and the offset luminance
value of the pixel located near the boundary of the other neighboring
divided regions are set to be a light-emitting efficiency and a offset
luminance value calculated based on the light-emitting efficiency and the
offset luminance value of the divided region including the pixel and the
light-emitting efficiency and the offset luminance value of the other
neighboring divided regions, instead of the light-emitting efficiency and
the offset luminance value of the each divided region. Thus, the
variations between pixels arranged near the boundary of the divided
regions can be reduced. Accordingly, it is possible to prevent the
boundary of the divided regions from appearing on screen, allowing a
display of a smoother image.

[0072] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the calculating of a
current-voltage characteristic of each pixel, when calculating the
light-emitting efficiency and the offset luminance value of the target
pixel, it may be that the closer the target pixel to the boundary with
the other neighboring divided region, the higher a ratio of the
light-emitting efficiency and the offset luminance value of the other
neighboring divided region used for the weighting.

[0073] According to this aspect, when calculating the light-emitting
efficiency and the offset luminance value of the target pixel, the
weighting is performed, increasing the ratio of the light-emitting
efficiency and the offset luminance value of the other neighboring
divided regions, as the closer the position of the pixel to the boundary
of the other neighboring divided regions. Accordingly, smoother images
can be displayed.

[0074] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the calculating of a
current-voltage characteristic of each pixel, when calculating the
light-emitting efficiency and the offset luminance value of the target
pixel, the light-emitting efficiency and the offset luminance value of
the target pixel may be calculated according to a ratio between a
distance from the target pixel to the center of the divided region
including the target pixel and a distance from the target pixel to the
center of each of the other neighboring divided region.

[0075] According to this aspect, when calculating the light-emitting
efficiency and the offset luminance value of the target pixel, the
light-emitting efficiency and the offset luminance value of the pixel are
calculated according to a ratio of the distance from the pixel to the
center of the divided region to which the pixel belongs to the distance
from the pixel to the center of the other neighboring divided region.

[0076] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the calculating of a
light-emitting efficiency and a offset luminance value, the
light-emitting efficiency and the offset luminance value calculated in a
method of fabricating another organic EL display apparatus fabricated
under a same condition may be used as the light-emitting efficiency and
the offset luminance value of each of the divided regions.

[0077] According to this aspect, the light-emitting efficiency and the
offset luminance value of each divided region calculated in the method of
fabricating an organic EL display apparatus can be used for the method of
fabricating another organic EL display apparatus fabricated under the
same condition as the organic EL display apparatus. Thus, it is possible
to omit the process for calculating the light-emitting efficiency and the
offset luminance value of the divided regions for each display panel,
each time the correction parameters for more than one display panel are
measured. Consequently, it is possible to shorten the fabricating process
of the apparatus.

[0078] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the obtaining of a
representative current-voltage characteristic, a representative
current-voltage characteristic obtained in a method of fabricating
another organic EL display apparatus fabricated under a same condition
may be used as the representative current-voltage characteristic.

[0079] According to this aspect, the representative current-voltage
characteristic calculated in the method of fabricating one organic EL
display apparatus can be used for the method of fabricating another
organic EL display apparatus fabricated under the same condition as the
organic EL display apparatus. Thus, it is possible to omit the process
for setting the representative voltage-current characteristic each time
the correction parameters for more than one display panel are measured.
Consequently, it is possible to shorten the fabricating process of the
apparatus.

[0080] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, writing, on a
predetermined memory used for the display panel, the correction parameter
for each pixel calculated in the calculating of a correction parameter.

[0081] According to this aspect, the correction parameter for each pixel
is written on a predetermined memory used for the display panel.

[0082] As described above, the display panel is divided into multiple
divided regions, and the light-emitting efficiency indicating the
characteristic common to each divided region is multiplied to each
current value in the representative current-voltage characteristic, and
the offset luminance value is added to the multiplied value so as to
calculate the luminance-voltage characteristic of each divided region.
Thus, the amount of correction by the correction parameter of each pixel
is smaller than in the case when the correction parameter is calculated
using the representative voltage-luminance characteristic common to the
entire display panel. Thus, the range of the values of the correction
parameters for the pixels can be made smaller, and it is possible to
reduce the bit count of the memory allotted to the value of the
correction parameter. As a result, it is possible to reduce the capacity
of the memory, lowering the fabrication cost.

[0083] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the obtaining of a
representative current-voltage characteristic, a plurality of voltages
may be applied to a plurality of pixels to be measured to flow current in
the pixels to be measured, the current flowing in each of the pixels to
be measured may be measured for each of the voltages, and the
representative current-voltage characteristic may be calculated by
averaging the current-voltage characteristics of the pixels to be
measured.

[0084] According to this aspect, the representative current-voltage
characteristic is calculated by applying multiple voltages to flow
current in the pixels to be measured, and by averaging the
current-voltage characteristics obtained for the pixels to be measured.
With this, only the current flowing in the pixels to be measured is
measured, instead of the current flowing in all of the pixels included in
the display panel. Thus, it is possible to significantly shorten the time
until the representative current-voltage characteristic common to the
entire display panel is set.

[0085] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, in the obtaining of a
representative current-voltage characteristic, a plurality of common
voltages may be simultaneously applied to the pixels to be measured to
flow current in each of the pixels to be measured, a sum of the current
flowing in the pixels to be measured may be calculated for each of the
common voltages, and the representative current-voltage characteristic
may be calculated by dividing the sum of the current flowing in the
pixels to be measured by the number of the pixels to be measured.

[0086] According to this aspect, the representative current-voltage
characteristic common to the entire display panel may be calculated by
applying common voltages to the pixels to be measured at one time,
measuring the sum of the currents flowing in the pixels to be measured,
and by dividing the sum of the measured currents by the number of the
pixels to be measured.

[0087] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, a correction parameter
may include a parameter indicating a ratio of a voltage of the
luminance-voltage characteristic of the target pixel calculated in the
calculating of a luminance-voltage characteristic to a voltage of the
luminance-voltage characteristic of the divided region including the
target pixel calculated in the calculating of a luminance-voltage
characteristic of each divided region.

[0088] According to this aspect, the correction parameter is set to be a
gain indicating luminance gain in the luminance-voltage characteristic of
the target pixel calculated in the calculating with respect to the
luminance-voltage characteristic in the divided region including the
target pixel calculated in the calculating.

[0089] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, a correction parameter
may include a parameter indicating a ratio of a luminance of the
luminance-voltage characteristic of the target pixel calculated in the
calculating of a luminance-voltage characteristic to a luminance of the
luminance-voltage characteristic of the divided region including the
target pixel calculated in the calculating of a luminance-voltage
characteristic of each divided region.

[0090] According to this aspect, the correction parameter is set to be a
gain indicating voltage gain in the luminance-voltage characteristic of
the target pixel calculated in the calculating with respect to the
luminance-voltage characteristic in the divided region including the
target pixel calculated in the calculating.

[0091] In the method of fabricating an organic EL display apparatus
according to an aspect of the present invention, a correction parameter
may include a parameter indicating a difference between a voltage of the
luminance-voltage characteristic of the target pixel calculated in the
calculating of a luminance-voltage characteristic and a voltage of the
luminance-voltage characteristic of the divided region including the
target pixel calculated in the calculating of a luminance-voltage
characteristic of each divided region.

[0092] According to this aspect, the correction parameter is set to be an
offset indicating the amount of voltage shift in the luminance-voltage
characteristic of the target pixel calculated in the calculating with
respect to the luminance-voltage characteristic in the divided region
including the target pixel calculated in the calculating.

[0093] Furthermore, the present invention produces the effects equivalent
to the effects described above, not only as the method of fabricating the
organic EL display apparatus including the characteristic steps, but also
as an organic EL display apparatus having the correction parameters
generated using the characteristic steps included in the method of
fabricating.

Embodiment 1

[0094] In this Embodiment, a fabricating process for generating a
correction parameter for correcting the unevenness in the luminance of
the display panel included in the organic EL display apparatus according
to the present invention, and storing the correction parameter in the
organic EL display apparatus shall be described. The stored correction
parameter is used in a display operation after the organic EL display
apparatus is shipped.

[0095] The following fabrication process includes (1) obtaining a
representative current-voltage characteristic common to an entire display
panel; (2) dividing the display panel into a plurality of divided
regions, applying voltage to the driving device in each of the pixels,
measuring a current flowing in each of the divided regions and luminance
of light emitted from the divided region when the current is flowing in
the divided region, calculating a current-luminance characteristic of the
divided region according to the measured current flowing in the divided
region and the measured luminance of the light emitted from the divided
region, and calculating a current-luminance conversion equation from the
current-luminance characteristic for each of the divided regions; (3)
measuring luminance of light emitted from each of the pixels by a
predetermined measuring device and calculating a luminance-voltage
characteristic of each of the pixels; (4) calculating a luminance-voltage
characteristic of each divided region by the representative
current-voltage characteristic and the current-luminance conversion
equation for the divided region; (5) calculating a correction parameter
for a target pixel such that the luminance-voltage characteristic of the
target pixel is corrected to the luminance-voltage characteristic of the
divided region including the pixel; and (6) writing, on a predetermined
memory, the correction parameter for each pixel calculated in the
calculating of a correction parameter. With this, it is possible to set a
constant current flowing in each light-emitting device for the same
specified gray-scale, making the current load constant between the
light-emitting devices. Thus, the chronological unevenness in the
light-emitting devices included in the display panel can be prevented.

[0096] The following shall describe the organic EL display apparatus and
the method of fabricating the organic EL display apparatus according to
the present invention shall be described with reference to the drawings.

[0097] FIG. 1 is a block diagram illustrating electric configuration of
the organic EL display device 1 according to Embodiment of the present
invention. The organic EL display apparatus 1 in FIG. 1 includes a
control circuit 12 and a display panel 11. The control circuit 12
includes a memory 121. The display panel 11 includes a scanning line
driving circuit 111, a data line driving circuit 112, and a display unit
113. Note that, the memory 121 may be provided inside the organic EL
display apparatus 1 and outside of the control circuit 12.

[0098] The control circuit 12 controls the memory 121, the scanning line
driving circuit 111, and the data line driving circuit 112. After the
completion of the fabricating process according to the fabricating method
described in Embodiment 1, correction parameters generated in the method
of fabricating the organic EL display apparatus according to the present
invention are stored in the memory 121. At the time of display operation,
the control circuit 12 reads the correction parameters written on the
memory 121, and corrects the video signal data input from outside, based
on the correction parameter, and outputs the corrected image signal data
to the data line driving circuit 112.

[0099] The control circuit 12 is also capable of driving the display panel
11 according to an instruction of an outside information processor by
communicating with the information processor during the fabricating
process.

[0100] The display unit 113 includes multiple pixels, and displays the
image based on the input video signal from outside to the organic EL
display apparatus 1.

[0101] FIG. 2 illustrates an example of circuit configuration of a pixel
in the display unit and a connection with circuits around the pixel. A
pixel 208 in FIG. 2 includes a scanning line 200, a data line 201, a
power supply line 202, a selection transistor 203, a driving transistor
204, an organic EL device 205, a holding capacitor 206, and a common
electrode 207. As the peripheral circuits, a scanning line driving
circuit 111 and a data line driving circuit 112 are provided.

[0102] The scanning line driving circuit 111 is connected to the scanning
line 200, and is capable of controlling conduction and non-conduction of
the selection transistor 203 for the pixel 208.

[0103] The data line driving circuit 112 is connected to the data line
201, and is capable of outputting the data voltage and determining the
signal current flowing in the driving transistor 204.

[0104] The selection transistor 203 has the gate connected to the scanning
line 200, and is capable of controlling the timing for supplying a data
voltage in the data line 201 to the gate of the driving transistor 204.

[0105] The driving transistor 204 functions as a driving device, and has
the gate connected to the data line 201 via the selection transistor 203,
the source connected to the anode of the organic EL device 205, and the
drain connected to the power supply line 202. With this, the driving
transistor 204 converts the data voltage supplied to the gate to a signal
current corresponding to the data voltage, and supplies the converted
signal current to the organic EL device 205.

[0106] The organic EL device 205 functions as a light-emitting device, and
the cathode of the organic EL device 205 is connected to the common
electrode 207.

[0107] The holding capacitor 206 is connected between the power supply
line 202 and the gate terminal of the driving transistor 204. The holding
capacitor 206 is capable of, for example, even when the selection
transistor 203 is turned off, maintaining the gate voltage immediately
before, and supplying the driving current from the driving transistor 204
to the organic EL device 205 continuously.

[0108] Note that, although not illustrated in FIGS. 1 and 2, the power
supply line 202 is connected to the power supply. The common electrode
207 is also connected to another power supply. The data voltage supplied
from the data line driving circuit 112 is applied to the gate terminal of
the driving transistor 204 through the selection transistor 203. The
driving transistor 204 passes a current according to the data voltage
between the source terminal and the drain terminal. This current flows
into the organic EL device 205 and the organic EL device 205 emits light
at a luminance according to the current.

[0109] Next, a fabricating system for implementing the method of
fabricating the organic EL display apparatus shall be described.

[0110]FIG. 3 is a functional block diagram illustrating the fabricating
system used for the method of fabricating the organic EL display device
according to the present invention. The fabricating system in FIG. 3
includes an information processor 2, an imaging device 3, an ammeter 4, a
display panel 11, and a control circuit 12.

[0111] The information processor 2 includes an operation unit 21, a
storage unit 22, and a communication unit 23, and is capable of
controlling the process until the correction parameter is generated. As
the information processor 2, a personal computer is applied, for example.

[0112] The imaging device 3 captures an image of the display panel 11
according to a control signal from the communication unit 23 in the
information processor 2, and outputs the captured image data to the
communication unit 23. A CCD camera or a luminance meter is used as the
imaging device 3, for example.

[0113] The ammeter 4 measures the current flowing in the driving
transistor 204 and the organic EL device 205 in each pixel, according to
the control signals from the communication unit 23 in the information
processor 2 and from the control circuit 12, and outputs the measured
current value data to the communication unit 23.

[0114] The information processor 2 outputs the control signals to the
control circuit 12, the imaging device 3, and the ammeter 4 in the
organic EL display device 1 through the communication unit 23, obtains
the measured data from the control circuit 12, the imaging device 3, and
the ammeter 4, stores the measured data in the storage unit 22, and
performs operations in the operation unit 21 based on the stored measured
data to calculate the characteristic values and parameters. Note that, a
control circuit not incorporated in the organic EL display apparatus 1
may be used as the control circuit 12.

[0115] More specifically, when setting representative current-voltage
characteristics (hereafter referred to as representative I-V
characteristics) which shall be described later, the information
processor 2 controls a voltage value to the measured pixel and the
ammeter 4 which measures the current flowing in the measured pixel, and
receives the measured current value. Note that, here, the imaging device
3 may not be provided. Furthermore, when measuring the current-luminance
characteristic (hereafter referred to as the I-L characteristic) of the
organic EL device which shall be described later, the information
processor 2 controls a voltage value to the pixel to be measured,
controls the imaging device 3, controls the ammeter 4, and receives a
measured luminance value and a measured current value. Furthermore, when
measuring the luminance-voltage characteristics (hereafter referred to as
L-V characteristics) of each pixel, the information processor 2 controls
a voltage value to the measured pixel, controls the imaging device 3, and
receives the measured luminance value.

[0116] The control circuit 12 controls a voltage value to the pixel 208 in
the display panel 11 by the control signal from the information processor
2. Furthermore, the control circuit 12 is capable of writing the
correction parameter generated by the information processor 2 to the
memory 121.

[0117] Next, the method of fabricating the organic EL display apparatus
according to the present invention shall be described.

[0118]FIG. 4 is an operational flowchart illustrating a method of
fabricating an organic EL display apparatus according to Embodiment 1 of
the present invention. FIG. 5A illustrates charts for illustrating
characteristics obtained by the first process group in the method of
fabricating the organic EL display device according to Embodiment 1 of
the present invention. FIG. 5B illustrates charts for illustrating
characteristics obtained by the second process group in the method of
fabricating the organic EL display device according to Embodiment 1 of
the present invention. FIG. 6 illustrates charts for illustrating
characteristics obtained by the third process group in the method of
fabricating the organic EL display device according to Embodiment 1 of
the present invention.

[0119]FIG. 4 illustrates process from generating an effective correction
parameter for correcting variations in luminance in the display panel
included in the organic EL display apparatus 1 to store the correction
parameter in the organic EL display apparatus 1. The effective correction
parameter is for mainly correcting the variations in the driving
transistors 204 so as to suppress chronological degradation of the
organic EL device 205. However, the correction parameter is generated
without measuring current in each pixel 208. In order to generate the
correction parameter, in this method of fabricating, the display unit 113
is divided into divided regions each includes multiple pixels 208, and
the I-L characteristic of each divided region is determined. Note that,
the divided regions are divided based on slight luminance inclination on
the display panel 11 caused by the fabrication process of the organic EL
device 205. Finally, correction parameters for the variations mainly due
to the variations in the driving transistors 204 are generated by
comparing the L-V characteristics for the divided regions each derived
from the I-L characteristics of the divided regions, and the L-V
characteristic of each pixel.

[0120] The following shall describe the fabricating process with reference
to FIG. 4.

[0121] First, the information processor 2 obtains and sets the
representative I-V characteristics common to the entire display unit 113
including multiple pixels each having the organic EL device 205 which is
a light-emitting device and the driving transistor 204 which is a driving
device which is voltage-driven and for controlling the supply of a
current to the organic EL device 205 (S01). FIG. 5A represents the
representative I-V characteristic common to the entire display unit 113.
The representative I-V characteristics is the characteristics of the
drain current corresponding to the voltage applied to the gate of the
driving transistor 204, and is nonlinear.

[0122]FIG. 7A is an operational flowchart illustrating the first specific
method for obtaining the representative I-V characteristics. In this
method, a pixel to be measured for determining the representative I-V
characteristics is extracted from the multiple pixels included in the
display unit 113. This pixel to be measured may be one pixel, or may be
more than one pixels selected based on a regularity or randomly selected.

[0123] First, the information processor 2 has the control circuit 12 to
apply a data voltage to the pixel to be measured such that a current
flows in the pixel, causing the organic EL device 205 in the pixel to
emit light (S11).

[0124] Next, the information processor 2 has the ammeter 4 to measure the
current in step S11 (S12). Steps 11 and 12 are repeated for more than
once for different data voltages. Steps 11 and 12 may be performed at the
same time for multiple pixels to be measured. Alternatively, steps 11 and
12 may be repeatedly performed for each pixel to be measured.

[0125] Next, the information processor 2 calculates the I-V
characteristics for each pixel to be measured by the operation unit 21,
based on the data voltage and the current corresponding to the data
voltage obtained in steps S11 and S12 (S13).

[0126] Next, the information processor 2 calculates the representative I-V
characteristics by averaging the I-V characteristics obtained for each of
the pixels to be measured (S14).

[0127]FIG. 7B is an operational flowchart illustrating the second
specific method for obtaining the representative I-V characteristics. In
this method, a pixel to be measured for determining the representative
I-V characteristics is extracted from the multiple pixels included in the
display unit 113. This pixel to be measured may be one pixel, or may be
more than one pixels selected based on a regularity or randomly selected.

[0128] First, the information processor 2 has the control circuit 12 to
apply a common data voltage to the pixels to be measured such that a
current flows in the pixels at the same time, causing the organic EL
devices 205 in the pixels to emit light at the same time (S15).

[0129] Next, the information processor 2 has the ammeter 4 to measure the
sum of currents flowing in the pixels to be measured in step S15 (S16).
Steps 15 and 16 are repeated for more than once for different data
voltages.

[0130] Next, the information processor 2 causes the operation unit 21 to
divide the sum of the current values calculated in Steps 15 and 16 by the
number of pixels to be measured (S17).

[0132] Calculating the representative I-V characteristics by the method
described in FIGS. 7A and 7B allows measuring the current only for the
pixels to be measured, instead of measuring the currents flowing in all
of the pixels included in the display unit 113. Thus, it is possible to
dramatically shorten the time necessary for setting the representative
I-V characteristics common to the entire display unit 113.

[0133] Note that, the first and second specific methods for obtaining the
representative I-V characteristics may not be performed for each organic
EL display apparatus according to the present invention. For example, the
representative I-V characteristics obtained in a method of fabricating
another organic EL display apparatus fabricated in the same condition may
be used as the representative I-V characteristics of the organic EL
display apparatus without modification. Accordingly, the representative
I-V characteristics calculated in the method of fabricating an organic EL
display apparatus is used in the method of fabricating another organic EL
display apparatus fabricated in the same condition as the organic EL
display apparatus. Therefore, it is possible to omit extra process
necessary for setting the representative I-V characteristics each time
the correction parameter of the display panels is measured. Consequently,
it is possible to shorten the fabricating process of the apparatus.

[0134] The following shall describe the fabricating process with reference
to FIG. 4 again.

[0135] Next, the information processor 2 divides the display panel into
multiple divided regions, applies voltage to the driving transistors 204
included in the pixels, measures current flowing in each divided region
and luminance of light emitted from the divided region to calculate the
I-L characteristic of each divided region, and calculates the I-L
conversion equation for each divided region from the I-L characteristic
(S02). By executing the step S02, the I-L characteristic of each divided
region illustrated in FIG. 5A (b) is obtained. This I-L characteristic
can be approximated by the following linear function using a slope p
defined as light-emitting efficiency and an offset luminance value q
which is the luminance-axis intercept of the I-L characteristic:

L=p*I+q (Equation 1)

The matrix illustrated in FIG. 5A (c) are coefficients of the I-L
conversion equation (p, q) in each divided region calculated by
approximating the I-L characteristic of the divided region by the
equation 1.

[0136]FIG. 8A is an operational flowchart illustrating the first specific
method of calculating the coefficients of the I-L conversion equation in
each divided region. In this method, a pixel to be measured for
determining the I-L characteristic of a divided region is extracted from
the pixels included in the divided region. This pixel to be measured may
be one pixel, or may be more than one pixels selected based on a
regularity or randomly selected. Alternatively, the pixels to be measured
may be all of the pixels included in the divided region.

[0137] First, the information processor 2 has the control circuit 12 to
apply a data voltage simultaneously to the pixels to be measured such
that a current flows in the pixel, causing the organic EL device 205 in
the pixel to emit light (S21).

[0138] Next, the information processor 2 instructs the ammeter 4 to
measure the current in step S21 (S22). Here, when the pixels to be
measured are all of the pixels in the divided region or the multiple
selected pixels, the sum of the current values is measured. Steps S21 and
S22 are repeated for more than once for different data voltages.

[0139] Next, the information processor 2 have the imaging device 3 to
capture the light emitted in step S21 (S23). Steps S21 to S23 are
repeated for more than once for different data voltages.

[0140] Next, the information processor 2 calculates the I-L characteristic
for each divided region by the operating unit 21 from the current and the
corresponding luminance obtained in steps S22 and S23, and calculates the
coefficients (p, q) in the I-L conversion equation described above for
each divided region (S24). Note that, when the pixels to be measured in
the divided region are all of the pixels in the divided region or
multiple selected pixels, the I-L characteristic for each divided region
is calculated using an average current value obtained by dividing the sum
of the current value by the number of pixels to be measured as I.

[0141]FIG. 8B is an operational flowchart illustrating the second
specific method of calculating the coefficients of the I-L conversion
equation in each divided region. The method described in FIG. 8B is
different from the method in FIG. 8A in that the steps S21 to S23 are
performed only once. This method is applied only when the I-L
characteristic is a primary expression passing the original point; that
is, only when it is assumed that the offset luminance value q is assumed
to be 0. In this method, a pixel to be measured for determining the I-L
characteristic of a divided region is extracted from multiple pixels
included in the divided region. This pixel to be measured may be one
pixel, or may be more than one pixels selected based on a regularity or
randomly selected. Alternatively, the pixels to be measured may be all of
the pixels included in the divided region.

[0142] Note that, the first and second specific methods for calculating
the coefficients of the I-L conversion equation in each divided region
may not be performed for each of the organic EL display apparatus
according to the present invention. For example, as the coefficients, the
coefficients in the I-L conversion equation for each divided region
obtained in the method of fabricating the organic EL display apparatus
manufactured under the same condition may be used as the coefficients for
the organic EL display apparatus without modification. With this, the
light-emitting efficiency and the offset luminance value of the each
divided region calculated by the method of fabricating an organic EL
display apparatus is used in the method of fabricating another organic EL
display apparatus fabricated under the same condition as the organic EL
display apparatus. Thus, it is possible to omit the extra process for
calculating the light-emitting efficiency and the offset luminance value
for each display panel each time the correction parameters for multiple
display panels are measured. Consequently, it is possible to shorten the
fabricating process of the apparatus.

[0143] The following shall describe the fabricating process with reference
to FIG. 4 again.

[0144] Next, the information processor 2 have the imaging device 3 to
measure the luminance of the light emitted from each pixel included in
the display unit 113, and calculates the L-V characteristics of each
pixel (S03). Here, if the L-V characteristics of each pixel is measured
by applying voltage to each pixel and measure the luminance, it is
necessary to measure the luminance for the number of times as much as the
number of the pixels, increasing the time for measurement and fabricating
cost. In this Embodiment, the L-V characteristics of each pixel can be
determined by a measurement for all of the pixels at once, without
performing the measurement for the number of times as much as the number
of the pixels.

[0145]FIG. 9A is an operational flowchart for describing a first specific
method for calculating the L-V characteristics for each pixel. FIG. 9B
illustrates the captured image when calculating the L-V characteristics
in each pixel.

[0146] First, the information processor 2 selects the color to be measured
(S31). In this embodiment, suppose that the display unit 113 includes
pixels 208 each having red (R), green (G), and blue (B) sub pixels.

[0147] Next, the information processor 2 selects the gray-scale to be
measured (S32).

[0148] Next, the information processor 2 applies the voltages according to
the selected gray-scales to all of the sub pixels in the selected color,
causing all of the sub pixels to emit light simultaneously (S33).

[0149] Next, the information processor 2 have the imaging device 3 capture
the light emitted from the entire sub pixels at the same time (S36). FIG.
9B illustrates an image captured by the imaging device 3 showing the
light-emitting state of the display unit 113 in a gray-scale, when red is
selected. The grid pattern on the entire diagram indicates unit pixels in
the light-receiving unit of the imaging device 3. Since the unit pixel in
the light-receiving unit of the imaging device 3 is sufficiently small
with respect to the captured sub pixels in R, the luminance of each of
the R sub pixel can be determined based on this image.

[0150] Next, the information processor 2 changes the gray-scale to be
measured (No in S38), and performs steps S33 and S36.

[0151] Furthermore, when steps S33 and S36 end in all of the gray-scales
to be measured (Yes in S38), the color to be measured is changed (No in
S39), and steps S32 to S38 are executed.

[0152] Furthermore, when steps S32 to S38 end for all of the colors (Yes
in S39), the information processor 2 obtains the images obtained in steps
S31 to S39, and determines the luminance of each pixel based on the
obtained image (S40). In this step, the luminance value of the pixel in
the region (2, 1) is calculated as an average value of output values of
the pixels in the imaging device belonging to the region (2, 1), for
example.

[0153] According to this method, when obtaining the L-V characteristics of
each pixel, the simultaneous light-emission of all of the sub pixels in
the light-emitting panel is captured at one time, without capturing light
emitted from each pixel by applying the predetermined voltage.
Subsequently, based on the captured image, the luminance of the light
emitted from each sub pixel is determined by image processing separating
the light emitted from each pixel. Accordingly, it is possible to
significantly reduce the time for capturing image, considerably
simplifying the process for obtaining the L-V characteristics for each
pixel.

[0154] FIG. 10A is an operational flowchart for illustrating the second
specific method of calculating coefficients for the L-V characteristics
for each pixel. FIG. 10B is a diagram for illustrating a captured image
when calculating the L-V characteristics for each pixel. Furthermore,
FIG. 10C is a state transition diagram of the measured pixels that are
selected. The method illustrated in FIG. 10A is different from the method
illustrated in FIG. 9A in that steps S34 and S37 are added. More
specifically, the method illustrated in FIG. 10A does not obtain the
captured image by simultaneously causing all of the corresponding sub
pixels to emit light in the selected color or selected gray-scale.
Instead, multiple captured images are obtained by causing the sub pixels
to emit light separately for multiple times. According to this method, it
is possible to avoid the interference of the light emitted from the
adjacent pixels, and to calculate highly precise luminance value of each
pixel.

[0155] Note that, the imaging device 3 used for calculating the L-V
characteristics for each pixel in FIGS. 9A and 10A is preferably an image
sensor, and is more preferably a CCD camera. With this, the image of
emitted light from all of the pixels can be obtained with low noise, high
sensitivity, and high resolution, allowing obtaining the highly precise
L-V characteristics for each pixel by image processing separating the
light emitted from each pixel.

[0156] The following shall describe the fabricating process with reference
to FIG. 4 again.

[0157] Next, when a pixel for which the correction parameter should be
generated is not at the boundary with the other divided regions to which
the pixel does not belong to (Yes in step S04), the information processor
2 calculates the L-V characteristic of the divided region by the
representative I-V characteristic set in step S01 and the I-L conversion
equation for the divided region to which the pixel belongs to calculated
in step S02. More specifically, using the representative I-V
characteristic representing the display unit 113, I in the I-L
characteristic in the divided region is converted to V by parameter
conversion, and the L-V characteristic for the divided region is
obtained.

[0158] The parameter conversion shall be specifically described using (d)
in FIG. 5B. For example, in the divided region matrix of the coefficients
(p, q) in (c) in FIG. 5A, the L-V characteristic of the top-left divided
region (coefficients (10, -2) is calculated as follows. First, the slope
p is multiplied to the parameter I of the representative I-V
characteristic. The offset luminance value q is added to the multiplied
value. With this, the parameter I in the representative I-V
characteristic is converted to L in the divided region. As described
above, the L-V characteristic in each divided region is calculated (S05).

[0159] Subsequently, the information processor 2 has the operation unit 21
calculate the correction parameter for correcting the I-V characteristics
of each pixel calculated in step S03 to the representative I-V
characteristics calculated in step S01, for each pixel (S06).

[0160] On the other hand, when the pixel for which the correction
parameter should be generated is near the boundary with the other divided
region to which the pixel does not belong to (No in step S04), the
information processor 2 calculates the target L-V characteristic which is
the target for calculating the correction parameter of the pixel from the
representative I-V characteristic set in step S01 and the I-L conversion
equation in the divided region to which the pixel belongs to, and the I-L
conversion equation for the other divided regions calculated in step S02.
The parameter conversion shall be specifically described with reference
to FIG. 11.

[0161]FIG. 11 is a diagram for illustrating a method of weighting
coefficients of pixels at the boundary of the divided regions. As
illustrated in FIG. 11, when the pixel 1 exists at the boundary region of
the divided regions 1 to 4, if the correction parameter is generated
using steps S05 and S06, the difference in luminance around the boundary
of the divided regions may be noticeable in the corrected image.
According to this method, when generating the correction parameter for
the pixel 1, the L-V characteristic for the correction target is the L-V
characteristic derived from the I-L characteristic with weighted slope p
and offset luminance value q among the adjacent divided regions, instead
of setting the L-V characteristic of the divided region 1 to which the
pixel 1 belongs to as the correction target L-V characteristic. More
specifically, the correction target L-V characteristic is calculated
using the coefficients (p1, q1) of the weighted I-L conversion equation
(S07). In FIG. 11, the coefficient p1 of the weighted I-L conversion
equation using the coefficients (p, q) in the adjacent divided regions 1
to 4 is

p1={(10+8)/2+(14+2)/2}/2=8.5 (Equation 2)

Furthermore, the coefficient q1 in the weighted I-L conversion equation
is

q1={((-2)+(-5))/2+((-3)+(-4))/2}/2=-3.5 (Equation 3)

[0162] Next, the information processor 2 calculates the correction target
L-V characteristic from the representative I-V characteristic set in step
S01 and the coefficients (p1, q1) in the I-L conversion equation weighted
in step S07. More specifically, using the representative I-V
characteristic representing the display unit 113, I in the weighted I-L
characteristic is converted to V by parameter conversion, and the
correction target L-V characteristic is obtained. In this case, in the
divided region matrix with the coefficients (p1, q1), I in the
representative I-V characteristic is multiplied by the slope p1. The
offset luminance value q1 is added to the multiplied value. With this,
the parameter I in the representative I-V characteristic is converted by
L of the correction target by parameter conversion. As described above,
the correction target L-V characteristic is calculated (S08).

[0163] Subsequently, the information processor 2 has the operation unit 21
calculate the correction parameter for correcting the I-V characteristics
of each pixel calculated in step S03 to the representative I-V
characteristics calculated in step S01, for each pixel (S09). By steps
S07 to S09, the variations between the pixels arranged near the boundary
of the divided regions can be reduced. Accordingly, it is possible to
prevent the boundary of the divided regions from appearing on screen,
allowing a display of a smoother image.

[0164] Note that, in step S07, when calculating the slope p1 and the
offset value q1 of the pixel to be corrected, it is preferable that the
weighting is performed such that the higher the ratio of the
light-emitting efficiency and the offset luminance value of the other
divided regions the closer the pixel is to the boundary of the other
divided regions.

[0165] Furthermore, in step S07, when calculating the slope p1 and the
offset luminance value q1 of the pixel to be corrected, the
light-emitting efficiency and the offset luminance value may be
calculated according to the ratio of the distance from the pixel to the
center of the divided region to which the pixel belongs to and the
distance from the pixel to the center of the other divided regions. The
weighting enables a display of a smoother image.

[0167]FIG. 12A is a graph illustrating luminance-voltage characteristic
when calculating correction values for voltage gain and voltage offset in
a method of fabricating the organic EL display apparatus according to
Embodiment of the present invention. In FIG. 12A, the correction
parameter includes a voltage gain indicating a ratio of a voltage value
of the L-V characteristic of the pixel to be corrected calculated in step
S03 and the voltage value of the divided region or the correction target
calculated in step S05 or step S08. Furthermore, the correction parameter
described in FIG. 12A includes the voltage offset indicating the
difference between the voltage value of the L-V characteristic in the
pixel to be corrected calculated in step S03 and the voltage value in the
L-V characteristic in the divided region or the correction target
calculated in step S05 or step S08.

[0168]FIG. 12B is a graph indicating the luminance-voltage characteristic
when calculating a correction value for the luminance gain in the method
of fabricating the organic EL display apparatus according to Embodiment 1
of the present invention. In FIG. 12B, the correction parameter includes
a luminance gain indicating a ratio of a luminance value of the L-V
characteristic in the pixel to be corrected calculated in step S03 to the
luminance value in the L-V characteristic of the divided region or the
correction target calculated in step S05 or step 508.

[0169] Note that, the correction parameter described above is not limited
to the combination illustrated in FIGS. 12A and 12B, but may include at
least one of three types; namely, the voltage gain, voltage offset, and
luminance gain.

[0170] The following shall describe the fabricating process with reference
to FIG. 4 again.

[0171] Finally, the information processor 2 writes the correction
parameter for each pixel calculated in steps S06 and S09 to the memory
121 in the organic EL display apparatus 1 (S10). More specifically, as
illustrated in (f) in FIG. 6, the correction parameters including (the
voltage gain and the voltage offset) for each pixel are stored
corresponding to the matrix of the display unit 113 (M rows×N
columns), for example.

[0172]FIG. 13A is a graph indicating the amount of offset and offset
width when a correction parameter is generated in the conventional
fabrication method. FIG. 13B is a graph indicating the amount of offset
and the offset width when a correction parameter is generated in the
method of fabricating the organic EL display apparatus according to
Embodiment of the present invention. In the method of fabricating the
organic EL display apparatus according to the present invention, the
light-emitting efficiency indicating the characteristic common to the
divided region is multiplied by each current value in the representative
current-voltage characteristic, and the offset luminance value is added
to the multiplied value so as to calculate the luminance-voltage
characteristic of the divided region. Accordingly, compared to the case
illustrated in FIG. 13A when the correction parameter is calculated using
the representative voltage-luminance characteristic as the correction
target, the amount of correction by the correction parameter of each
pixel described in FIG. 13B is small. Accordingly, the range indicating
the value of the correction parameter for each pixel (the offset width in
the drawing) is small, and thus it is possible to reduce the bit count of
the memory allotted to the value of the correction parameter. As a
result, it is possible to reduce the capacity of the memory 121, lowering
the fabricating cost.

[0173] According to the conventional method of generating the correction
parameters, the luminance-voltage characteristics of each pixel
calculated by measuring the luminance of the light emitted from the pixel
included in the display panel reflects both the variations in the organic
EL device and the variations in the driving transistor. When a correction
parameter for correcting both of the variations is calculated and the
image signal from outside is corrected using the correction parameter,
the correction includes the corrections to the variations in the organic
EL device. Accordingly, this correction makes the luminance of the light
emitted from the organic EL device uniform with respect to the image
signal having the same gray-scale for the entire display panel.

[0174] However, due to the variations in the characteristics of the
organic EL device, the luminance when the same current flows is different
between the organic EL devices. Accordingly, the amount of current
flowing in each pixel is different. Accordingly, in this case, due to the
fact that the product life of the organic EL device depends on the amount
of current, the product life of each light-emitting device varies as the
time passes. The variation in product life consequently appears as uneven
luminance on screen.

[0175] In response to this problem, in this Embodiment, only the variation
in driving transistor is corrected, maintaining the amount of current
flowing into the organic EL devices for the image signal of the same
gray-scale at the same value. This is because, although the variations in
the driving transistors between the devices are large, the variations in
the organic EL devices between the devices are very small, and thus
correcting only the variations in the driving transistors enables
displaying of a uniform image to human eye without correcting variations
in the organic EL devices.

[0176] According to this Embodiment, the L-I characteristics of the
divided region including the pixels to be corrected is the
characteristics including the variations in the organic EL devices.
Accordingly, converting the L-V characteristics of the pixel to be
corrected to the I-V characteristics of each pixel using the L-I
characteristics of the divided region including the pixels to be
corrected means calculating the correction parameter for mainly
correcting the variations in the driving transistor.

[0177]FIG. 14 illustrates the effect of the organic EL display apparatus
corrected by the method of fabricating the organic EL display apparatus
according to the present invention. The display panel in the organic EL
display apparatus before correction has a luminance distribution
reflecting both the luminance distribution due to the organic EL device
and the luminance distribution due to the driving transistor. In
contrast, according to the method of fabricating the organic EL display
apparatus according to the present invention, the variations in the
driving transistors are mainly corrected. Accordingly, in the display
panel after the correction, although the luminance inclination due to
variations in the organic EL devices remains, it is possible to maintain
the current flowing into each organic EL device constant with respect to
the specified same gray scale, setting the current load between the
organic EL devices constant. Accordingly, it is possible to set the
current flowing into each organic EL device constant, suppressing the
variation in the product life of each light-emitting device included in
the display panel as time passes. As a result, it is possible to prevent
the uneven luminance due to the variations in the product life of the
light-emitting device from appearing on screen. Note that, the luminance
inclination due to the variation in the organic EL device remains in the
display panel after the correction is the luminance inclination which
cannot be detected by human vision.

[0178] Furthermore, according to this Embodiment, the L-V characteristics
including both the variations in the organic EL devices and the
variations in the driving transistors in each pixel and the
light-emitting efficiency and the offset luminance value of each of the
divided regions are measured in order to obtain the correction parameter
for correcting the variations in the driving transistors, instead of
measuring the variations of the driver transistors themselves in the
pixels. In other words, the light-emitting efficiency and the offset
luminance value of each divided region is calculated by dividing the
display panel into multiple divided regions, and measuring the current
flowing in the divided region and the luminance of the divided region
when the current is flowing in the divided region. In other words, by
calculating the light-emitting efficiency and the offset luminance value
of each divided region, it is possible to clarify the variations in the
light-emitting devices between the divided regions. This is because; the
organic EL device varies for a predetermined region, rather than for each
pixel. Furthermore, the L-V characteristic of each pixel allows measuring
the pixels at the same time using a CCD camera, for example. With this,
compared to the case in which the variations in the driving transistor is
measured by applying voltage to each pixel, and measuring the variation
in the driving transistor by measuring the current flowing in each pixel,
it is possible to significantly reduce the time for measuring the
correction parameter.

[0179] Note that, in the method of fabricating the organic EL display
apparatus according to the present invention, the display panel is
divided into the divided regions. However, it is preferable that the
division reflects the luminance inclination due to the variations in the
characteristics of the organic EL devices.

[0180] FIG. 15A indicates luminance distribution on a display panel when
the light-emitting layer is formed by vapor deposition. When the
light-emitting layer is formed by vapor deposition, the thickness of
light-emitting layer at the central part of the display unit 113
increases, and thus a concentric-circular thickness distribution is
formed. Accordingly, the light-emitting efficiency and the offset
luminance value of the organic EL device have a concentric-circular
distribution. In this case, by dividing the divided region into the
concentric-circular shape as shown in FIG. 15A, consequently, it is
possible to obtain highly precise correction parameter for mainly
correcting the variation in the driving transistors 204.

[0181] FIG. 15B indicates the luminance distribution on the display panel
when the light-emitting layer is formed by inkjet printing. When scanning
the ink-jet head and printing the light-emitting layer on the display
unit 113, the light-emitting efficiency changes in the scanning direction
due to difference in environment at the time of drying the ink and
others. Furthermore, the amount of injection from a nozzle of an ink-jet
heat mildly varies in the longitudinal direction of the ink-jet head.
Thus, the light-emitting efficiency varies in a direction vertical to the
scanning direction. When the distribution of light-emitting efficiency is
not monotonous as in this example, it is preferable that the divided
region should be divided in small regions. As a result, it is possible to
obtain the highly precise correction parameter for mainly correcting the
variation in the driving transistor.

Embodiment 2

[0182] In Embodiment 2, a case in which the organic EL display apparatus
has the display panel to perform display operation using a correction
parameter generated by a method of fabricating the organic EL display
apparatus according to the present invention.

[0183]FIG. 16 is a drawing for illustrating the operations for correcting
the voltage gain and the voltage offset at the time of display operation
in the organic EL display apparatus according to Embodiment 2 of the
present invention.

[0184] The control circuit 12 reads a correction parameter (voltage gain,
voltage offset) stored in Embodiment 1 from the memory 121, and the data
voltage corresponding to the video signal is multiplied by the voltage
gain, the voltage offset is added to the multiplied value, and the
calculated value is output to the data line driving circuit 112. This
allows the currents flowing in each of the organic EL devices constant
with respect to the specified same gray scale, setting a constant current
load on the organic EL devices. Accordingly, it is possible to set the
current flowing into each organic EL device constant, suppressing the
variation in the product life of each light-emitting device included in
the display panel as time passes. As a result, it is possible to prevent
the uneven luminance due to the variations in the product life of the
light-emitting device from appearing on screen.

[0185] FIG. 17 is a drawing for illustrating the operations for correcting
the voltage gain at the time of display operation in the organic EL
display apparatus according to Embodiment 2 of the present invention.

[0186] The control circuit 101 corrects and converts the video signal
input from outside to a voltage signal corresponding to each pixel. The
memory 102 stores the luminance gain and the representative LUT
corresponding to each pixel unit.

[0187] The control circuit 101 in FIG. 16 includes a correction block 601
and a conversion block 602. When an input of the video signal from
outside is received, the correction block 601 reads the luminance gain in
row a, column b from the memory 102 with respect to the input current
signal in row a and column b, and corrects the luminance signal. The
conversion block 602 converts the corrected luminance signal to the
voltage signal in row a and column b corresponding to the video signal,
based on the representative conversion curve stored in the memory 102.
The correction block 601 includes a pixel position detecting unit 611, a
video-luminance conversion unit 612, and multiplying unit 613, and the
conversion block 602 includes a luminance-voltage conversion unit 614 and
a driving circuit timing controller 615.

[0188] The pixel position detecting unit 611 detects pixel position
information of the video signal by a synchronization signal
simultaneously input with the video signal from outside. Here, it is
assumed that the detected pixel position is row a and column b.

[0189] The video-current conversion unit 612 reads, from the
video-luminance conversion LUT stored in the memory 102, a luminance
signal corresponding to the video signal.

[0190] The multiplying unit 613 corrects the luminance signal by
multiplying the luminance gain corresponding to each pixel unit stored in
the memory 102 in Embodiment 1 with the luminance signal. More
specifically, the luminance gain k in row a and column b is multiplied by
the luminance signal value in row a and column b, generating the
luminance signal in row a and column b after correction.

[0191] Note that, the multiplying unit 613 may correct the luminance
signal by a calculation other than multiplication such as a division of
the luminance gain corresponding to each pixel unit stored in the memory
102 in Embodiment 1 by the luminance signal obtained by converting the
video signal input from outside.

[0192] The luminance-voltage conversion unit 614 reads the voltage signal
in row a and column b corresponding to the corrected luminance signal in
row a and column b output from the multiplying unit 613 from the
representative LUT derived from the representative conversion curve
stored in the memory 102.

[0193] Finally, the control circuit 101 outputs the converted voltage
signal in row a and column b to the data line driving circuit 112 through
the driving circuit timing controller 615. The voltage signal is
converted to an analog voltage and input to the data line driving
circuit, or converted to an analog voltage in the data line driving
circuit. Subsequently, the converted signal is supplied to each pixel
from the data line driving circuit 112 as the data voltage.

[0194] According to Embodiment 2, the video signal input from outside is
converted to the luminance signal for each pixel unit by the correction
block 601 and the conversion block 602, and the luminance signal for each
pixel unit is corrected to the predetermined reference luminance. After
that, the luminance signal in each pixel unit is converted into a voltage
signal, and outputs the converted voltage signal is output to the driving
circuit of the data line.

[0195] With this, the data stored for each pixel unit is the luminance
gain corresponding to each pixel unit and the luminance gain for setting
the luminance of the video signal corresponding to each pixel unit to the
predetermined reference luminance. Accordingly, it is not necessary for
preparing a conventional luminance signal-voltage signal conversion table
for converting the luminance signal corresponding to the video signal to
the voltage signal for each pixel unit, and the amount of data prepared
for each pixel unit can be significantly reduced. In addition,
predetermined information regarding the representative conversion curve
indicating the voltage-luminance characteristics common to the pixel
units are held in common with the pixel units. This is a fraction of
amount of data.

[0196] Accordingly, it is possible to significantly reduce the amount of
data necessary for correcting the current varying for each pixel unit of
the display panel to obtain the video signal having the luminance common
to the entire screen. Therefore, the manufacturing cost is significantly
reduced. As a result, it is possible to reduce the manufacturing cost and
the processing load at the time of driving, implementing an even display
on the entire screen.

[0197] Furthermore, the predetermined information indicating the
representative conversion curve corresponding to the voltage-luminance
characteristic common to the pixel units is one, common to the pixel
units, and thus the memory capacity can be reduced to minimum.

[0198] Here, the luminance gain used in the correction block 601 is a
correction parameter generated in the method of fabricating the organic
EL display apparatus according to the present invention and stored in the
memory. The representative conversion curve may be the representative I-V
characteristic set in step S01 in the method of manufacturing the organic
EL display apparatus according to the present invention.

[0199] With this, even when the luminance gain is set as the correction
parameter as illustrated in FIG. 17, it is possible to set a same current
flowing in the light-emitting devices for the same specified gray-scale,
making the current load constant between the light-emitting devices.
Accordingly, it is possible to set the current flowing into each organic
EL device constant, suppressing the variation in the product life of each
light-emitting device included in the display panel as time passes. As a
result, it is possible to prevent the uneven luminance due to the
variations in the product life of the light-emitting device from
appearing on screen.

[0200] Although only some exemplary embodiments of the organic EL display
apparatus and the method of manufacturing the organic EL display
apparatus according to the present invention have been described in
detail above, those skilled in the art will readily appreciate that many
modifications are possible in the exemplary embodiments without
materially departing from the novel teachings and advantages of this
invention. Accordingly, all such modifications and appliances including
the organic EL display apparatus according to the present invention are
intended to be included within the scope of this invention.

[0201] For example, the organic EL display apparatus according to the
present invention and the method of fabricating the organic EL display
apparatus are incorporated in a thin flat TV as illustrated in FIG. 18.
The organic EL display apparatus and the method of manufacturing the
organic EL display apparatus allows an implementation of low-cost thin
flat television having a long-life display with uneven luminance
suppressed.

[0202] Furthermore, in the embodiments 1 and 2, the term "voltage" in the
representative current-voltage characteristics (representative I-V
characteristics) and the luminance-voltage characteristics (L-V
characteristics) may not only refer to an analog voltage value, but also
a voltage signal representing a gray-scale. More specifically, in the
embodiments 1 and 2, the representative current-voltage characteristic
(representative I-V characteristic) and the luminance-voltage
characteristic (L-V characteristic) include a representative
characteristic between a current and a voltage signal and a
characteristic between a luminance and a voltage signal, respectively.

[0203] Although only some exemplary embodiments of this invention have
been described in detail above, those skilled in the art will readily
appreciate that many modifications are possible in the exemplary
embodiments without materially departing from the novel teachings and
advantages of this invention. Accordingly, all such modifications are
intended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

[0204] The present invention is particularly useful for an organic EL flat
panel display including an organic EL display apparatus, and is suitably
used as a display apparatus of a display which requires uniform image
quality and the method of manufacturing the display apparatus.